A series of Ce x Zr 1−x O 2 mixed-oxide-supported Ru catalysts were unprecedentedly evaluated in the catalytic wet air oxidation (CWAO) of 2-chlorophenol (2-CP) solutions (2gL −1 ). They were shown to exhibit higher performances than the corresponding CeO 2 or ZrO 2 -supported catalysts. The ceria–zirconia solid solution structure appeared to be crucial for the higher activity of the 3wt.% Ru/Ce x Zr 1−x O 2 catalysts. After introduction of praseodymium or neodymium in the Ce x Zr 1−x O 2 lattice, the activity of the 3wt.% Ru/Ce x Zr 1−x O 2 catalysts was further improved. Pr was shown to have a greater effect than Nd, especially at low Pr concentration. Further investigations indicated that Ce x Zr 1−x O 2 solid solutions loaded Ru catalysts could maintain outstanding catalytic performances even at low temperature (393K) and low pressure (3MPa).